In recent years, diagnosis based on images has been widely adopted. For example, an X-ray computed tomography (CT) device is used to produce tomographic images of a subject so as to construct three-dimensional image data representing the interior of the subject. The three-dimensional image data is used to diagnose a lesion.
As far as the CT system is concerned, while an X-ray irradiation and detection unit is continuously rotated, a subject is continuously moved in the direction of the body axis. Thus, helical scanning is performed on the three-dimensional field of the subject, and a three-dimensional image is produced based on tomographic images that represent successive sections of the subject in the three-dimensional field.
One of such three-dimensional images is a three-dimensional image representing the bronchi in the lungs. The three-dimensional image of the bronchi is utilized in order to three-dimensionally grasp the position of an abnormality that is suspected to be, for example, a pulmonary carcinoma. In order to check the abnormality through biopsy, a bronchoscope is inserted in order to collect a sample of a tissue using a biopsy needle located in the distal section of the endoscope.
FIG. 31 shows a bronchi 500. As far as an intracorporeal lumen that branches out in multiple stages is concerned, when the position of an abnormality is close to the terminal of a branch, it is hard to lead the distal end of an endoscope to a target region accurately for a short period of time. For example, Japanese Unexamined Patent Application Publication No. 2000-135215 has proposed a system for navigating a bronchoscope to a target region. Herein, a three-dimensional image of an intracorporeal lumen of a subject is constructed based on image data acquired from a three-dimensional field of the subject. The course to a target point along the lumen is determined using the three-dimensional image. Virtual endoscopic images representing regions of the lumen that lie along the course are constructed based on the image data, and displayed in order to navigate a bronchoscope.
However, the navigation to a target region to be performed in the system described in the Japanese Unexamined Patent Application Publication No. 2000-135215 includes display of a live endoscopic image produced by the bronchoscope. In addition, virtual endoscopic images representing branch points of bronchi are displayed for the purpose of guiding the bronchoscope into a destination of insertion. As mentioned above, the bronchi branch out in multiple stages. Moreover, images constructed with the bronchoscope located in the respective bronchi are images representing a plurality of branch destinations and resembling one another. When virtual endoscopic images are merely displayed, even if the virtual endoscopic images represent branch positions different from actual branch positions represented by a live endoscopic image, an operator may misidentify the virtual endoscopic images as images representing the correct branch positions. The misidentification may become a serious obstacle to navigation of the bronchoscope to a target region.
The present invention attempts to break through the foregoing situation. An object of the present invention is to provide an endoscope device capable of reliably navigating an endoscope to a target region using guide images that represent actual branch positions.